Alex Salmond has described the BBC’s coverage of the Scottish independence referendum as a disgrace, as he hit back at outgoing political editor Nick Robinson’s attack on “Putin-like” protests against the corporation.

Broadcasters are expected to press ahead with the TV election debates and believe they have legal grounds to “empty-chair” the Tories on the basis that they turned down a reasonable invitation to attend.

Downing Street has issued a “final offer” to broadcasters over the election television debates, declaring in a pointed email that David Cameron will take part in just one debate featuring seven party leaders before the formal campaign begins next month.